Control mechanism



March 15, 1938.

w. o. LUM 2,111,431

CONTROL MECHANISM Filed March 31, 1934 Inventor: Wa Pier 0. Lum

b9 M 8. 2M

His Attorney.

Patented Mar. 15, 1938 PATENT OFFICE oomor. MECHANISM Walter 0. Lum,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application March 31, 1934, Serial No. 718,395

8Claims.

My present invention relates to control mechanisms, particularly safetycircuit control switches and to furnace control systems embodying safetycircuit control switches. One of the objects is to provide an improvedmechanism for transmitting motion whereby a safety control switch may beoperated from one -control position to another in response either to asingle reciprocation of a given amplitude of a reciprocating mo- .10tion transmitting element or to a series of reciprocationsof lesseramplitude of the element. Another object is to embody such a safetycontrol switch mechanism in a furnace control system.

.15 In order that the principles underlying my invention may be clearlyunderstood I have described and illustrated different embodimentsthereof in a control switch mechanism and also described and illustratedthe manner in which such switch mechanism may be embodied in a furnacecontrol system.

In the operation of oil burner equipment there is danger of conditionsarising such that abnormal pressures, sometimes of an explosive nature,

will develop in the combustion chamber. It has been the practice toprovide safety doors or like vent means to relieve these abnormalpressures. Since such abnormal pressures are due to improper functioningof the burner mechanism, it

so is desirable to deenergize the fuel supplying apparatus and controltherefor immediately upon the occurrence of the abnormal pressure, andmechanism for effecting such deenergization of the oil burner equipmentin response to abnormal pressures forms the subject matter of mycopending application, Serial No. 596,067, filed March 1, 1932 andassigned to the assignee of the present invention. In the apparatustherein described, a safety switch, connected to an explosion reliefdoor by means of a chain or like connection, is automatically operatedto stop operation of the fuel supplying apparatus and control thereforin response to actuation of the relief door by pufiback or otherabnormal pressure conditions within the combustion chamber.

There also may occur in the operation of oil burner equipment, improperoperating conditions which will not be of such nature as to causeabnormal pressure of explosive proportions but which will causeirregularly recurring pulsations of abnormal pressure of relativelysmall magnitude. It has been found in the operation of an oil burnerapparatus equipped with safety mechanismsuch as described in my abovereferred to application, that such small mutations of abnormal pressurewill cause the pressure release door to vibrate to an extent sufilcientonly to allow the escape of puffs of undesirable fumes without beingsufficient to completely operate the safety switch to open-circuitposition. In other words, the amplitudes of the successive outwardmovements of the door, which is biased to return to closed position,will not be sumcient to move the elements of the safety switch asufficient distance with respect to each other to disengage them. It isdesirable, however, to deenergize the oil burner equipment upon theoccurrence of such relatively small pulsating abnormal pressures as wellas upon the occurrence of abnormal pressures of explosive proportions,since both denote improper operation of the burner equipment. A furtherand more specific object of my invention is, therefore, the provision ofimproved, simple and reliable control mechanism for insuringdeenergization of an oil burner equipment upon either a single openingof theoil burner pressure relief door to a predetermined degree or aseries of openings of the door to lesser degrees.

Fig. 1 is a schematic showing of an oil burner furnace, partially cutaway, to which my invention is applied; Fig. 2 is a detailed perspectiveshowing of the elements of one embodiment of my invention; and Figs. 3,4, and 5 illustrate successive steps in the operation of the mechanismshown in Fig. 2. Figs. 6, 7, and 8 illustrate another embodiment of myinvention and successive steps in the operation thereof, and Fig. 9illustrates schematically the manner of applying this last embodiment toan oil burner furnace similar to that shown in Fig. 1.

Referring to the drawing, an oil burner furnace I0 having a combustionchamber ii, is equipped with a motor operated pump and compressor unitI2 for supplying fuel and air to an atomizing nozzle 13. The combustionmixture discharged from the nozzle into the combustion chamber isignited by means of electrodes 14 and the products of combustion passfrom thence through the stack breaching l5 into the smoke pipe it whichleads to the stack. A pressure relief port I1 is incorporated in the topof the stack breeching, and a pressure relief door 20, pivotally mountedon the breeching as shown at 2 I, is biased by means of spring 22 toclose the relief port.

Electrical energy for the operation of the burner mechanism and theelectrodes is supplied from lines 23, 24 through a safety switch whichis shown at 25 as consisting of a terminal box 26 secured to the stackbreeching by means of mounting plate 21 and provided with a socket II towhich the electrical leads from lines a, 24 are brought by means ofconduit 2!. A movable switch element in the form of a plug 80 havingcontacts II, II. is provided for bridging the terminals in the socket20.

In accordance with my present invention, a one-way force transmittingmechanism is provided for connecting the door with the contact carryingplug it and for efi'ecting disengaging movement of the plug either in asingle step in response to opening of the door to a predetermineddistance or in a series of steps in response to a series of openings ofthe door to lesser distances. The principal element of this mechanism isa link member, in the form of a hook-shaped segment II. pivotallymounted at 83 upon clamp I4 secured to the free end of the door It. Thesegment engages a slotted stirrup I. attached to the plug Ill and isarranged to depend from the pivotal mounting with its free end extendingthrough the slot and its inner face 31 in frictional engagement with theunderneath side of the closed end of the slot in the stirrup. This innerface 31 of the segment is in the form of an irreversible cam surface.successive points of which as illustrated by points a and b, are atprogressively shorter distances from the pivot point If, and thereforefrom the free end of the door 20. It is preferred that the cam surfacebe continuous for reasons hereinafter to be set forth. A weight ll isamxed to the hook-shaped segment at some point horizontally oflset fromthe vertical line of motion of the pivot point It so that it willprovide a relatively large gravitational force acting about the leverarm, consisting of the portion of the segment between the weight and thepivot point, to tend to swing the segment in a counterclockwisedirection as viewed in Figs. 2 to 5 inclusive.

In the operation of the oil burner equipment conditions may arise in thecombustion chamber which will produce abnormal pressures of sumcientmagnitude to blow open the door 20. When the door is blown open by apufi'back, explosion or similar large abnormal pressure the movementthereof will be suflicient to disengage the contacts II and II of theplug 30 from the terminals in the socket 28 in a single stroke todeenergize the oil burner and ignition equipment. It will be apparentthat upon upward movement of the door 20 the frictional engagement ofthe inner surface of the hook-shaped segment 35 with the end of thestirrup 36 will become a positive engagement to provide a positiveoperating connection between the door and the movable plug so thatoutward movement of the door will pull the plug upward a distanceproportional to the amplitude of the movement of the door, and a singleopening of the door to a predetermined degree will be sufilcient tocompletely disengage the contacts of the safety switch 25.

There might also arise in the operation of the oil burner conditionssuch that pulsating pressures of small magnitude may occur within thecombustion chamber, and these pulsations will be sumcient to impart tothe pressure relief door only a vibratory opening movement such thateach upward movement of the door will be of insufiicient amplitude tocompletely disengage the contacts of the safety switch 25. Suchconditions are, of course, undesirable since they denote improperoperation of the oil burner equipment and will also allow continuedescape of combustion gases from the pressure relief port into the spacesurrounding the oil burner furnace. Hence it is desirable to have theoil burner equipment deenergized after repetition of this pulsatingcondition for a certain length of time. Figs. 8, 4, and 5 illustrate intwo steps the operation of the safety switch in response to vibration ofthe pressure release door 20, but it is to be understood that this ismerely illustrative and that it may take a much larger number ofsuccessive steps to completely disengage the contacts of the safetyswitch. When the door 20 is at rest in closed position and the plug IIis completely seated in the socket 28 which is the normal condition forproper operation of the furnace, a point on the cam surface 31 having aconnection distance denoted a will engage the stirrup 38. Upon a slightupward movement of the door Ill due to a pulse tion of abnormal pressurethe plug III will be caused to follow the movement of the door II inproportion to the extent of opening thereof. This will effect a partialdisengagement of the plug contacts from the terminals of the box It asshown in Fig. 4. Now upon return of the door to its closed position,were it not for the weight II the segment would tend to retain itsoriginal position as shown in the dotted lines of Fig. 4, and would tendto push the plug back into the socket in the terminal box 20. However,the biasing effect of the weight ll tends to cause the segment to rotatein a counterclockwise direction. thus forcing a succeeding bearing pointof the cam surface into engagement with the stirrup I, such successivebearing point having a connection distance such as b which is shorterthan that of the connection distance a of the bearing point which firstengaged the stirrup ll. This will produce a shorter connection distancebetween the door and the plug 30 so that succeeding upward movements ofthe door will produce added increments of upward movement of the plugand will eventually efi'ect complete disengagement of the contacts 8|and 32 from the terminals oftheterminalbox It asillustratedin Fig. 5. Itwill thus be seen that my improved linkage mechanism provides means forimparting progressive increments of movement to the movable switchelement or plug 30 upon successive vibration of the pressure relief door20, and that a predetermined summation of the outward movements of thedoor will effect complete disengagement of the safety switch todeenergize the electrical circuit of the oil burner and ignitionequipment. It is also apparent that the continuity of the cam surfaceprovides for infinitely small changes in connection length so that themechanism will function regardless of the amplitude of movement of thedoor.

Figs. 6 to 9 inclusive illustrate a modified form of my inventionwherein the linkage mechanism is particularly adapted for use withapressure relief door having substantially horizontal movement. Theoperating link in this embodiment is in the form of a closed segment 4|having an inner bearing face ll similar to the irreversible cam surfaceI! of the link ll in the embodiment first described. A weight 42 ofarcuate shape similar to that of a portion of the segment is riveted orotherwise fastened to the segment as shown at II and 4 Terminal box 20is incorporated in the wall of the furnace l0, and the socket therein isfiush with the wall. Plug 30 is provided with one or more projectingears 45 for engagement with the inner surface of the segment. Thesegment is end of rod 41 which passes through an opening 48 in theadjacent side of the stack breeching and through the interior thereof tothe opposite side where it is fastened to the pressure relief door 50which is arranged to close the port I in the wall of the breeching.Guide means 52 are provided to steady the rod and aid in holding it andthe door in position, and spring means 53 are provided to bias the doorin closed position.

The operation of the mechanism of the embodiment last described issimilar to that described in connection with Figs. 2 to 5 inclusive.Under normal conditions in the furnace, the pro- :Iection 45 will beengaged by a bearing point on the cam surface which has a connectiondistance a. Outward movement of the door 50 will cause the rod 41 toslide in the guides 48 and 52. This will cause segment 40 to pull on theplug 30 and eifect partial disengagement of the contacts 3| and 32 to anextent proportional to the distance of opening of the door, as forinstance, to a position such as shown in Fig. 7. Subsequent return ofthe door to closed position releases the frictional force between thebearing surface 4i of the segment and the projection 45, and allows thesegment to swing in a counter-clockwise direction under the influence ofweight 42 until a succeeding bearing point having a shorter dis tance,such as b, is forced into engagement with the projection. Thus,successive outward vibrations of the door impart progressive incrementsof movement to the movable switch member or plug and will completelydisengage the contacts of the plug from the terminals in the terminalbox, as shown in Fig. 8, after a predetermined summation of saidincrements of movement. when the plug is completely disengaged it willhang suspended from the segment by means of the projecting ear 45 whichwill rrst upon the lower portion of the segment 40, and the plug must bemanually reset to reestablish the energizing circuit of the oil burner.It will be evident that the link may be made in the form of twosegments, having similar contours, fixedly secured to each other inspaced apart side by side relation and pivotally mounted on oppositeends of the pivot pin 46, and the bearing surfaces of these two segmentsmay be arranged to engage projecting ears 45 on opposite sides of theplug 30.

From the foregoing description it will be seen that by my invention Ihave provided a mechanism for greatly increasing the safety andreliability of operation of an oil burner furnace. The embodiments ofthe invention herein illustrated and described have been selected forthe purpose of setting forth the principles involved. It will be aparent, however. that the invention is susceptible of being modified tomeet different conditions of use and that its use is not limited to aswitching mechanism for an oil furnace safety switch but maybe employedwith equal advantage in any situation where a control mechanism havingsimilar characteristics is desired. Such modifications are believed tobe within the spirit and scope of my invention and are intended to becovered by the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:-

1. The combination with a furnace having a combustion chamber,electrically operated fuel burnermeans therefor and an energizingcircuit for said electrically operated means, of electrical switch meansmovable between two circuit controlling positions to control theenergization of said circuit, a pressure relief door normally biased toclosed position and arranged to open different distances in response toabnormal pressures of different magnitudes within the combustionchamber, and means for effecting either continuous movement of theswitch means from one of said circuit controlling positions to the otherin response to a single opening of the door to a predetermined distanceor step by step movement of the switch means from said one circuitcontrolling position to the other in response to a series of lesseropenings of the door.

2. The combination with a furnace having a combustion chamber,electrically operated fuel burner means therefor and an energizingcircuit for said electrically operated means, of electrical switch meansmovable between two circuit controlling positions to control theenergization of said circuit, a pressure relief door normally biased toclosed position and arranged to have different degrees of opening inresponse to abnormal pressures of different magnitudes within thecombustion chamber, and means interconnecting the door and the switchmeans including a one-way force transmitting mechanism for effectingmovement of the switch means from one of said circuit controllingpositions to the other in response either to a single opening of thedoor to a predetermined degree or to a predetermined summation ofopenings of the door to lesser degrees.

3. The combination with a furnace having a combustion chamber,electrically operated fuel burner means therefor and an energizingcircuit for said electrically operated means, of switch means movablebetween two circuit controlling positions to control the energization ofsaid circuit, movable pressure responsive means operatively associatedwith the furnace to vibrate in response to pulsating abnormal pressureswithin the furnace combustion chamber, and means interconnecting thepressure responsive means and the switch means for effecting progressivemovement of the switch means from one of said circuit controllingpositions to the other in response to repeated vibration of the pressureresponsive means due to repeated pulsations of abnormal pressure in thecombustion chamber.

4. The combination with a furnace having a combustion chamber,electrically operated fuel burner means therefor and an energizingcircuit for said electrically operated means, of switch means operableto control the energization of said circuit and means for insuringdeenergization of said circuit upon the occurrence of pulsating abnormalpressures in the combustion chamber including a pressure relief dooroperatively associated with the furnace and vibratorily movable inresponse to said pulsating abnormal pressures, biasing means for holdingthe door normally in closed position, and means intercom necting thedoor and the switch means including a one-way force transmittingmechanism for imparting progressive increments of movement to saidswitch means toward open circuit position in response to a series ofsuccessive vibrations of the door due to said pulsating abnormalpressures.

5. In combination, electric circuit controlling means having a switchelement movable between two circuit controlling positions, and means fortransmitting motion to said element including a movable element and aone-way force transmitting mechanism interconnecting said switch elementand movable element for effecting movement of the switch element fromone to the other of said circuit controlling positions in respouse toeither a single movement of said movable element through a predetermineddistance or the repeated movement 0! the movable element through alesser distance.

6. In combination, circuit controlling means having a switch elementmovable between two circuit controlling positions, and means fortransmitting motion to said element including a reciprocating element,and a one-way iorce transmitting mechanism mechanically interconnectingsaid switch element and said reciprocating element for moving saidswitch element from one to the other oi said circuit controllingpositions in response to either a single reciprocation oi thereciprocating element through a predetermined distance or a series ofreciprocations of said reciprocating element through a lesser distance.

7. In combination, circuit controlling means having a switch elementmovable between two circuit controlling positions, and mechanism fortransmitting motion to said element including a pair oi members having aone way interlocking engagement for movement thereof as a unit with saidswitch and biased to have relative movement therebetween in the oppositeway to provide a movable connection of varying lengths with the switchelement.

8. In combination, circuit controlling means having a switchelementmovable between two circuit controlling positions, and mechanismfor transmitting motion to said element including a pair oi relativelymovable members, one being pivotally mounted and having a one wayinterlocking engagement with the other member and biased to successivelyshorten the distance between the mounting point of said one member andthe other member upon reciprocation done 01 said members to eiiectprogressive increments of movement of the switch element between saidpositions.

WALTER 0. LOB.

